The NICHD's Pediatric Pharmacology Research Units (PPRU) coordinating center provides a full range of administrative support for the Institute's the PPRU network of 13 clinical sites. The PPRU clinical sites and the coordinating center facilitate and promote pediatric [unreadable]labeling[unreadable] (Food and Drug Administration (FDA) approval) of new drugs and drugs already on the market, by conducting clinical trials and related translational research in pediatric therapeutics. Currently, a large percentage of drugs prescribed in the U.S. for infants and children are used [unreadable]off label,[unreadable] because data on their safety and efficacy, and appropriate dosages and formulations for children, are lacking or inadequate. For pediatric labeling, the effects of child development on the pharmacokinetics of drugs, the influence of age-specific changes in drug disposition and pharmacodynamics, or the interplay between disease states in children and their stage of development, must all be investigated. Network consultation and coordinating with the FDA is ongoing and the PPRU also strives to foster cooperative research efforts among academia, industry, and health professionals. The coordinating center serves as a central point of contact for participating sites, to facilitate communication and responsiveness.